Screenshot from ULA Webcast of the launch of NROL-35. It's cold, windy and dark. Just you wait
Mission Rundown: ULA - Atlas V 541 - NROL-35
Written: January 16, 2023
That’s Thirty Five. Carry the one
United Launch Alliance has conducted its final launch of 2014, making use of a new upper stage engine on its Atlas V rocket to deliver a NRO payload into orbit.
Friday’s launch of NROL-35 dodged the weather and occurred on December 12/13, 2014 at 19:19 PST - 03:19 UTC from Space Launch Complex 3E at Vandenberg Air Force Base.
Although mission details are classified, the rocket was believed to be targeting a Molniya orbit – a highly elliptical trajectory with a period of 12 hours slowly hovering over Russian polar regions most of the time. The orbit is named after Molniya communication satellites which were the first spacecraft from the Soviet Union to make use of it.
The Atlas V flew in her 541 configuration, however her Centaur upper stage sported the RL10C engine for its first time in space. 455th time for all the engine types.
Notam crash sites for 5 SRB’s 250 km, fairing parts 1200 km and core booster 3200 km ±100 km. Distances were measured using Google Earth. Centaur upper stage has a site south of Tasmania.
From notices to airmen, or NOTAM’s, issued to ensure flight safety along the launch corridor. These show that the rocket flew along a south-south-easterly azimuth along the Pacific coasts of California and Mexico, consistent with the approximately-63-degree Molniya orbit. NOTAM for NROL-35 resemble those issued on previous launches.
As is normal for National Reconnaissance Office spacecraft, NROL-35’s mission has not been disclosed. The likely use of a Molniya orbit, however, suggests that it will either be used for communications or signals intelligence (SIGINT).
The NROL-35 Payload
The Quasar satellites in Molniya orbit are ageing – the two most recent launches occurred in 2004 and 2007 with the third-youngest spacecraft having launched in 1998 – however it has been speculated that the NRO may be moving towards an all-geostationary Quasar constellation, with the last three satellites all going to geostationary orbit.
The Molniya orbit is a special class of Highly Elliptical Earth Orbit, with an orbital period of approximately twelve hours and inclination of about 63.4 degrees. Most of that time is spent looking down on Russia looking for multiple missile launches. Two satellites usually take turns working together with relay of data to a third geostationary satellite.
NROL-35 are in addition to its regular signal intelligence gathering equipment also hosting a set of instruments, the SBIRS payload consisting of a 273 kg ~ 600-lb infrared scanning sensor with 3 colors in short-wave, mid-wave, and see-to-ground sensor chip assemblies in two short Schmidt telescope cameras mounted in a 2-axis agile precision gimbal.
The observation mount can point and control the dual optical telescopes pointing towards any target on Earth for close up Strategic and wide Theater Surveillance. Hidden from direct sunlight the Schmidt telescopes have a passive thermal cooling of the cameras, which increases the sensitivity of the sensor chip assemblies inside.
A computer control system with its own dish antenna capable of downloading 100 Mbps of data to ground station receiver antennas or relayed to geostationary SBIRS satellite for direct downlink to large US military dish antennas.
The SBIRS data stream is managed by the Remote Sensing Systems Directorate at the U.S. Air Force Space and Missile Systems Center with the 460th Space Wing at Buckley AFB in Aurora, Colorado in daily control.
The Atlas V 541 Launch
The flight profile for Friday’s launch wasn’t announced, however like any Atlas V mission it began with ignition of the RD-180 engine powering the first stage around 2.7 seconds before launch. Ignition of the four Aerojet solid rocket motors attached to the first stage and liftoff occurred at around T+1.1 seconds.
The solids burned for about 95 seconds, remaining attached for a little longer after burnout to avoid dropping debris in restricted areas where they may pose a danger to shipping or oil drilling. Fairing separation occurred midway through first stage flight.
The mission coverage ended at that point, due to the nature of the mission. However, first stage flight ended with Booster Engine Cutoff (BECO), a little over four minutes after liftoff, with the RD-180 shutting down. First stage separation occurred six seconds later, with second stage ignition about ten seconds after that.
The second stage of the Atlas V is a Centaur, which is powered by one RL10 engine depending upon mission requirements – to date every Atlas V launch has used the single-engine version.
While Atlas V launches to date have used an RL10A-4-2 engine to power the Centaur, Friday’s mission introduced the new RL10C-1. The RL10C-1 and RL10C-2 are intended to replace the Atlas’ RL10A and Delta IV’s RL10B-2 engines respectively with a single common design.
Derived from the RL10B series, which was spun off in the 1990s for Delta upper stages beginning with the short-lived Delta III, the RL10C also incorporates more modern production processes to reduce the cost of assembly and provide greater standardization across ULA’s fleet.
Trumpet satellites are inserted directly into Molniya orbits, unlike Quasar satellites which are deployed into lower orbits and then maneuver to their operational orbits under their own power. Because of this, Centaur is expected to perform two burns; one to achieve a low Earth parking orbit, and a second to reach the final deployment orbit.
Amateur satellite watchers, via the Seesat-L mailing list, are predicting that NROL-35 will separate into an orbit of around 1,120 by 37,600 kilometers (696 by 23,400 miles, 604 by 20,300 nautical miles), with an inclination of 63.56 degrees. Shortly after launch the spacecraft will likely maneuver to its operational orbit.
The Atlas V 541 Rocket
The Atlas V is an expendable medium lift launch system and member of the Atlas rocket family. The rocket is one of the most reliable in the world, having 50 launches with only one partial failure and no complete failures.
The Atlas V 541 rocket, tail no. AV-051 is standing 59.7 meters - 196 feet tall on SLC-3E.
The rocket has two stages. The first is a Common Core Booster (CCB), which is powered by an RD-180 engine with two bells and burns kerosene (RP-1) and liquid oxygen (LOX). This is accompanied by up to five strap-on solid rocket boosters. The second stage is the Centaur upper stage, which is powered by the first RL10C rocket engine which burns liquid hydrogen (LH2) and liquid oxygen (LOX).
Atlas V rocket is filled with 344 472 liter - 91 000 gallons of RP-1, liquid oxygen and liquid hydrogen. How much goes to fill each stage and the four main propellant tanks. Together they can contain 344,47 m3 RP-1, cryogenic oxygen and cryogenic hydrogen.
Atlas V 541 split in its major parts. This is a generic non mission specific graphic configuration
The Common Core Booster holds 184 728 liter - 48 800 gallon liquid oxygen chilled to below -182,96 0C Celsius or -297,33 0F Fahrenheit that can fit in a 184,73 m3 oxygen tank.
The Common Core Booster holds 94 635 liter - 25 000 gallon RP-1 highly refined kerosine at room temperature that can fit in a 94,64 m3 fuel tank.
The Centaur upper stage holds about 49 400 liter - 13 050 gallons of liquid hydrogen chilled to -252,8 0C Celsius or -423 0F Fahrenheit that can fit in a 49,40 m3 hydrogen tank.
The Centaur upper stage holds about 15 709 liter - 4 150 gallons of liquid oxygen chilled to below -182,96 0C Celsius or -297,33 0F Fahrenheit that can fit in a 15,71 m3 fuel tank.
Data on Helium gas, pressures used and number of COPV to store it. And there is a tank to store propellant used for maneuvering during ascent and in orbit.
HAZ GAS operations are completed - That command is given when the 150 kg hydrazine is loaded. The RCS thrusters on the Centaur stage are using hydrazine as a monopropellant during orbit insertion and maneuvering.
The reaction control system (RCS) includes the ullage pressure thrust from the tanks and consists of twenty hydrazine monopropellant engines located around the stage in two 2-thruster pods and four 4-thruster pods. For propellant, 150 kg (340 lb) of Hydrazine is stored in a pair of bladder tanks and fed to the RCS engines with pressurized helium gas, which is also used to accomplish some main engine start up functions.
In the 541 configuration, the Atlas V is capable of carrying up to 14,067 kg to Low Earth Orbit (LEO), and 8,290 kg to Geostationary Transfer Orbit (GTO).
The Atlas V 541 rocket has a three number configuration code.
The first number represents the fairing diameter size in 4 or 5 meters, so in this instance there is a 5 meter fairing.
The fairing, which is manufactured by RUAG of Switzerland, comes in three different lengths, with this launch using the shortest of these. This measures 20.7 meters (68 feet) in length, while the exact diameter is 5.4 meters (17.7 feet).
As well as encapsulating the payload, the five-meter fairing also encloses the rocket’s second stage, the 10 feet wide Centaur. This encapsulation of Centaur is dangerous on account of hydrogen leaking because it's so volatile. Making a lot of ventilation holes in the lower half of the fairing reduces that danger.
The second number denotes the number of solid rocket boosters (SRBs), which attach to the base of the rocket. The number of SRBs for a 5 meter fairing can range from 0 – 5. In this case there will be 4 SRB’s attached to the center core.
The third number shows the number of engines on the Centaur Upper Stage, which is 1 in this configuration. So this means that this rocket will have a 5 meter fairing, 4 solid rocket boosters, and 1 engine bell on the Centaur Upper Stage.
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